The present invention relates to a valve assembly for a fluid control device. Particularly, the present invention relates to a pressure balance unit for the valve assembly.
Valve assemblies are used in a variety of plumbing fixtures for controlling the temperature and volume of water dispensed from the fixture. A valve assembly may receive hot water and cold water from separate supply lines and controllably mix the water to provide an output having an intermediate temperature. Temperature control may be accomplished by restricting the volumetric flow rate of either the hot water or the cold water into a mixing chamber within the valve assembly. Typical valve assemblies control volumetric flow rate by increasing or decreasing a cross-sectional area through which either the hot water or the cold water may flow. A user-operable handle, dial, or other mechanism may be used to increase or decrease a cross-sectional area of a flow path within the valve assembly.
Another factor affecting volumetric flow rate is water pressure. The water pressure in the supply lines correlates with a velocity of the water through the valve. Contemporary valve assemblies may include a pressure balance unit for balancing the water pressure of the hot and cold water supply. A pressure balance unit may be used to ensure that differences in water pressure between the hot water supply and cold water supply do not affect the temperature of the mixed output. For example, without a pressure balance unit, if the water pressure in the cold water supply line were to suddenly drop (e.g., a toilet is flushed elsewhere within the plumbing system), the volumetric flow rate of cold water through the valve assembly would decrease, thereby increasing the temperature of the mixed output and potentially providing unexpected hot water to a user (e.g., in the shower). A pressure balance unit may sense a difference in water pressure and decrease the volumetric flow rate of the hot water proportionately, thereby maintaining the mixed output at a constant temperature.
Federal, state, and municipal regulations, as well as consumer demand, are encouraging the use of plumbing fixtures that use less water. Thus, there is a need for an improved pressure balance unit that can operate effectively under low-flow conditions.